Name	Name	Last commit message	Last commit date
parent directory ..
README.md	README.md

Functions 1 ~ 7

1) What is function? What is the difference between function and Method?

Answer:

Function / Method is a block of statements which performs some specific task.
Function is global whereas Method is associated with a Class and Structure.

// Global Scope
// Function Example
func function() {
	print("I'm a Function")
}

function()

// Method
class Car {
	func method() {
		print("I'm a Method beloing to `Car`")
	}
}

let car: Car = Car(
car.method()

2) What is `inout` parameter in Swift?

The input arguments of a method by default are let constants. To change the value of input arguments the input keyword helps.
To pass the references of the arguments to a method we use inout keyword.

// Without `inout`
class Car {

	func refuel(input: Double) {
		input += 10 // Error, because `input` here is `Constant`
	}

}

// With `inout`
class Car {

	func refuel(input: inout Double) {
		input += 10 // It works!
	}

}

// parameter with `&`
let car: Car = Car()
let baseValue: Double = 20.0
car.refuel(input: &baseValue)

3) Instance method vs Type Method?

Methods are two types: Instance methods and Type Methods.
Instance methods are tied up with the instance of a class. So access instance methods using object.
Type methods are tied up with classes. Use ClassName. TypeMethod.
Use static / class to declare Type Methods

class SomeClass {

	class func typeMethod() {
		print("This is TypeMethod")
	}

	static func staticMethod() {
		print("Another type of TypeMethod")
	}

	func method() {
		print("This is method")
	}

}

let someClass: SomeClass = SomeClass()

// call method
someClass.method()

// call type method
someClass.typeMethod()
someClass.staticMethod()

4) What is the difference between `class func` and `static func` ?

Answer:

class function — can be overridden, but static func cannot be overridden

class MyClass {

// Instance Method
func instanceMethod() {}

// Class Type Method
class func classTypeMethod() {}

// Static Type Method
static func staticTypeMthod() {}

}

// Common
MyClass.classTypeMethod()
MyClass.staticTypeMethod()

// Difference
class SubMyClass: MyClass {

	// Good!
	override class func classTypeMethod() {}

	// Compile Error
	override static func staticTypeMthod() {}

}

#Tips

if you use class type method with final keyword, there is no difference using static type method.

5) What is variadic number of params method?

Answer:

A method which accepts dynamic number of input arguments is known as variadic params method.

class MyClass {

	func variadicMethod(numbers: Int...) {
		print(numbers)
	}

}

let myClass: MyClass = MyClass()
myClass.variadicMethod(numbers: 1)
myClass.variadicMethod(numbers: 1, 2)
myClass.variadicMethod(numbers: 1, 2, 3)

6) How to set default value to a method input arguments?

Answer:

func myName(firstName: String, lastName=”Shin”)

class MyClass {

	func defaultValueMethod(a: Int, b: Int = 10) {
		print("a: \(a)")
		print("b: \(b)")
	}

}

let myClass: MyClass = MyClass()
myClass.defaultValueMethod(a: 10) // a: 10, b: 10
myClass.defaultValueMethod(a: 5, b: 3) // a: 5, b: 3